Summary: A new study reveals that UV exposure can increase appetite while simultaneously preventing weight gain. This unexpected finding is attributed to UV’s influence on hormones and neurotransmitters, leading to increased energy expenditure and the browning of subcutaneous fat. These insights could pave the way for innovative approaches to combat obesity and metabolic disorders.
Key Facts:
- UV exposure increases appetite but surprisingly prevents weight gain.
- UV rays trigger the release of norepinephrine, increasing energy expenditure.
- UV radiation induces the browning of subcutaneous fat, further boosting energy burning.
Source: Elsevier
Obesity and metabolic disorders are increasingly significant global public health issues.
In a novel study, a team of dermatologists evaluated the effect of ultraviolet (UV) exposure on appetite and weight regulation. They found that UV exposure raises norepinephrine levels, decreases leptin levels, and induces the browning of subcutaneous fat, thereby increasing energy expenditure.
These results potentially pave the way for new approaches to prevent and treat obesity and metabolic disorders.
Their findings appear in the Journal of Investigative Dermatology, published by Elsevier.
UV radiation is a common environmental factor that has multifaceted effects on the skin, which encompasses a substantial surface area of the body. UV radiation induces detrimental effects such as sunburn, photoaging, and skin cancer; however, it is also associated with beneficial effects such as vitamin D synthesis.
Co-first authors Qing-Ling Quan, MD, PhD, and Eun Ju Kim, PhD, Department of Dermatology, Seoul National University Hospital, explained, “Recent evidence has suggested that UV exposure limits body weight gain in mouse models of obesity. Subcutaneous fat is a critical organ in regulating energy homeostasis.
“Alongside previous studies on the effects of UV exposure on obesity and metabolic disorders, our team was inspired by our prior discovery that, although UV rays do not directly reach subcutaneous fat when exposed to the skin, they can regulate the metabolism of subcutaneous fat.
“This led us to hypothesize that skin exposure to UV rays could play a significant role in systemic energy homeostasis, prompting this research.”
Investigators discovered that when exposed to UV radiation consistently, mice fed a normal diet and those on a high-fat diet exhibited increased appetite due to a decrease in leptin, a key hormone in appetite regulation. However, there was no weight increase.
They found that UV radiation inhibits weight gain by enhancing secretion of the neurotransmitter norepinephrine, which not only decreases leptin but also increases energy expenditure through the “browning” of subcutaneous fat.
The increased energy intake, driven by heightened appetite, is converted to heat and burned before it can accumulate in subcutaneous fat, thus preventing weight gain.
This research provides new insights into the impact of UV exposure on appetite and weight regulation, opening possibilities for novel approaches in the prevention and treatment of obesity and metabolic disorders.
Specifically, uncovering the mechanism by which UV radiation prevents weight gain could offer new approaches to dietary regulation and weight loss, providing innovative insights into health and obesity management that could positively impact human health.
Lead investigator Jin Ho Chung, MD, PhD, Department of Dermatology, Seoul National University Hospital, Seoul National University College of Medicine, explained, “This study elucidates the mechanism by which UV exposure can increase appetite while inhibiting weight gain.
“These findings contribute significantly to understanding the effects of UV radiation on energy metabolism and homeostasis and open new avenues for exploring prevention and treatment strategies for obesity and metabolic disorders.
“Notably, the fact that UV radiation lowers leptin levels and increases norepinephrine, thereby promoting the browning of subcutaneous fat and increasing energy expenditure, provides a groundbreaking clue for the development of obesity treatment strategies.
“This research demonstrates that UV exposure not only affects the skin but also plays a deep role in our body’s energy metabolism and homeostasis processes.
“However, further research is needed on the long-term effects and safety of UV exposure, and there should be significant interest in developing new therapeutic approaches that utilize the efficacy of UV radiation.”
However, as co-corresponding author Dong Hun Lee, MD, PhD, Institute of Human-Environment Interface Biology, Seoul National University, noted, “Because UV exposure can accelerate skin aging and promote skin cancer, it is advisable to minimize UV exposure and protect the skin with sunscreen.
“Thus, our research team plans to conduct follow-up studies to develop new strategies that could mimic the effects of UV radiation for obesity and metabolic regulation.”
About this appetite and neuroscience research news
Author: Eileen Leahy
Source: Elsevier
Contact: Eileen Leahy – Elsevier
Image: The image is credited to Neuroscience News
Original Research: Open access.
“UV Irradiation Increases Appetite and Prevents Body Weight Gain through Upregulation of Norepinephrine in Mice” by Jin Ho Chung et al. Journal of Investigative Dermatology
Abstract
UV Irradiation Increases Appetite and Prevents Body Weight Gain through Upregulation of Norepinephrine in Mice
UV irradiation of the human skin downregulates lipid synthesis and adipokine production in subcutaneous fat. Recent evidence has suggested that UV exposure limits body weight gain in mouse models of obesity.
However, the relationship between norepinephrine and UV irradiation has not been previously reported. Chronic UV exposure stimulated food intake but prevented body weight gain.
Leptin, an appetite-suppressing hormone, was significantly reduced in the serum of the UV-irradiated mice. In contrast, UV irradiation induced browning of subcutaneous white adipose tissues without increasing physical activity.
Notably, UV irradiation significantly increased norepinephrine levels, and the inhibition of norepinephrine production reversed the effects of chronic UV irradiation on food intake and body weight gain.
In conclusion, chronic UV irradiation induces norepinephrine release, resulting in the stimulation of food intake due to the downregulation of leptin levels, but it prevents weight gain by inducing the browning process and elevating energy expenditure.
